Is it possible to define the width of the columns in saved search results?

you can’t set them per se, but you can make the column label longer and that will expand (or reduce) the size. You can use <br> on the label to stack word if needed.

How can I make the column longer? Some data under the columns are wrapped and we want to expand the column so they won't be.

you need long column labels, or you can add spaces after your label text.